As described in U.S. Pat. Nos. 4,321,943 and 4,798,224, a considerable amount of thermal energy may be wastefully dissipated from hot water lines which provide hot water to plumbing fixtures, such as domestic wash basins, dishwashers and clothes washers. This thermal energy is generated from heating sources utilizing fuels such as heating oil, coal, natural (petroleum) gas, and electric heating means (which may ultimately use any one of these fuels, as well as hydraulic, wind and solar generating sources to generate the electricity).
In addition, if water is allowed to run down the drain while waiting for hot water to be delivered to the fixture from a remote hot water source, a substantial water loss may occur. As droughts have become more and more frequent, water loss can become costly, and can contribute to water shortages in various localities.
In order to reduce such water loss, plumbing systems have been devised which continuously circulate hot water from a hot water source to the fixture and back to the hot water source. In such systems, a supply of hot water is always readily and quickly available at a given plumbing fixture despite the remote position of the hot water source. As a result, the water loss is then limited to the amount of cold water disposed in draw pipes interconnecting the plumbing fixture to the hot water conduit in which hot water is circulated.
While such systems substantially reduce the amount of water which must be withdrawn from the fixture before suitable hot water is obtained, they are not energy efficient because the array of pipes interconnecting the plumbing fixtures in the hot water source provide an enormous surface area for thermal radiation therefrom. Such thermal radiation requires continual reheating of the water in the hot water lines to compensate for to heat loss. In addition, the electrical cost of running a circulating pump may cause such system to be prohibitive in view of the energy conscious requirements of many local, state and federal governmental agencies.
Thermal losses in both circulating and non-circulating plumbing systems have been reduced by the installation of insulation to the exterior of the hot water lines as well as to the heating source (e.g., hot water heaters, boilers, and the like) that feed the plumbing fixtures with hot water. While such insulation can slow the dissipation of heat, no savings occur over an extended period of time in non circulating systems because intermittent use of hot water through the lines still allows hot water to cool to ambient temperatures. In constantly circulating systems, of course, there is a continual thermal loss.
With specific reference to noncirculating systems, devices have been developed to actually recover the hot water remaining in the hot water lines after the use of a fixture by drawing the hot water back into the hot water tank; e.g., see U.S. Pat. Nos. 4,321,943 and 4,798,224. Because hot water is removed from the lines in such systems, there is an actual reduction in the amount of heat loss rather than just a slowing of heat loss as occurs through the use of insulation alone.
U.S. Pat. No. 5,042,524, is directed to an accelerated hot water delivery system which substantially reduces thermal losses by providing intermittent, rather than constant, circulation of heated water through the hot water lines. The hot water circulation may be initiated by any suitable means, such as, a timer, a motion sensor or wall switch located close to the plumbing fixture.
In some systems in which the hot water is either constantly or intermittently recirculated, particularly those installed in newly constructed buildings, a dedicated hot water recirculating line may be installed. This dedicated recirculation line begins and terminates at the hot water source, and feeds hot water via a recirculation pump to each plumbing fixture through a series of feeder lines. This permits hot water to quickly flow from the hot water line to a given fixture when the tap, shower or appliance is used.
In some other systems, such as the system described in U.S. Pat. No. 5,277,219, the cold water line may be used as a return line for a hot water loop by connecting the hot water line to the cold water line and utilizing a pump that is able to generate a sufficient head to overcome the water pressure in the cold water line; such utilization of the cold water line to recirculate hot water shall be termed “cross-connection” herein. Additionally, particularly when the pump is not a positive displacement type pump, a one way valve is very preferably disposed between the hot water and cold water lines to prevent heated water from being circulated through the pump to the cold water lines after the heated water is delivered to the fixture in question. Typically, the valve is, e.g., a solenoid type valve hardwired to the controller. This enables an instant hot water system to be readily retrofitted into existing homes without the need for the installation of a separate dedicated return line to the hot water heater.
In the past number of years “on command” instant hot water systems have undergone a change in sophistication as computers and mobile computing devices such as, without limitation, computers, smart phones, tablet computing devices, key fobs and the like have become a tool from which multiple appliances and devices, in the home and in the office, can be controlled. U.S. Pat. No. 9,513,019 is drawn to an on-command hot water system in which a remote computer, including a mobile computing device, may be used to control the operation of, and to receive information from and concerning, the instant hot water system, either through direct “wired” connections such as Etherenet, or by wireless connections.
Wireless technology has been proposed for hot water recirculation. Thus, Bell & Gossett makes a wireless recirculation kit called the ecocirc wireless Potable Hot Water Recirculation Kit, which includes a recirculation pump and an under-sink cross connection system in which hot and cold water lines are connected. A battery-operated wireless valve opens to permit recirculation of hot water until a pre-set temperature threshold is reached at a temperature sensor within the valve. The valve then sends instructions to the pump to stop recirculating hot water. See Instruction Manual, available at http://bellgossett.com/pumps-circulators/circulator-pumps/potable-water-circulators/ecocirc-wireless-instant-hot-water-system/, accessed Oct. 30, 2017.
Each and every patent, patent publication and item of non-patent literature cited in this specification is hereby individually incorporated by reference in its entirety.